The present invention relates to a system for the production of mechanical energy from a plurality of heat sources at different temperatures. A particularly suitable application for a system of the present invention is in the recovery of heat from a heat engine such as an internal combustion engine running on gasoline or diesel oil. Such engines produce excess heat which is usually merely dissipated by a coolant system and thereby wasted. Moreover the exhaust gases emitted by such engines enter the atmosphere at high temperatures but the heat of such gases is again merely allowed to dissipate and be wasted. This is true not only of engines used in automobiles, but also heavy commercial engines used in shipping and even the large scale motors used for the central generation of electricity. All this waste heat could be turned into useful mechanical energy if suitable systems for doing this were available but until the present invention there was no system for converting the heat from several heat sources at different temperatures into useful mechanical work.